Process of converting cast-iron into iron or steel.



' NITED STATES PATENT OFFICE.

PAUL LOUIS TOUSSAINT HE IItOULT, OF LA PRAZ, FRANCE, ASSIGNOR TO SOCIETEELECTRO METALLURGIQUE FRANQAISE, OF FROGES,

IsERE, FRANCE.

PROCESS OF CONVERTING CAST-IRON INTO IRON OR STEEL.

Specification of Letters Patent.

Patented Dec. 12, 1905.

Application filed May 19, 1903. Serial No. 157,863.

To all whom it may concern:

such as refining, purification, reduction, car= crucible or furnace.

buriz ation, the addition of metals or alloys,

&c., which are concerned in obtaining the desired product-are conductedin an electric According to the presentinvention high-gradeorcruciblesteel, by which I mean steel of a high degree of purity andgenerally, but not necessarily, of a high carbon contentsuch, forexample, as is generally used for the making of the special steelscontaining manganese, nickel, &c., hereinafter referred to-is made fromcast-iron or the like by first refining it by oxidation in the usual orany suitable manner and then transforming it in the electric furnaceinto the desired product. -The first apparatus may be a converter of theBessemer kind or an oxidizing-furnace of any kind. To facilitate thisexplanation, it may be assumed that a basiclined Bessemer converter isto be used analogous to those usually employed for dephosphorizing. Sideby side are arranged the converter and the electric furnace, the latterbeing, for example, of the oscillating kind already described in aprevious patent, (No. 707,776, dated August 26, 1902.)

The first part of the operations which is conducted in the converterconsists in treating the molten cast-iron of the first or second fusioncontaining more or less carbon, silicon, manganese, sulfur, phosphorus,&c., so as to refine it by oxidation according to the usual method. Thisoxidation operation is stopped at a point suitable for the succeedingoperations-for example, when the content of the molten metal in carbonhas been reduced to between 0.02 and 0.05 per cent. When phosphoric pigis being treated, the oxidation is pushed furthernamely, until thephosphorus has been practically completely oxidized and has passed intothe basic slag formed by the addition of basic material, such as isusually added in the basic process. The slag formed is then removednearly completely by tilting the converter. refined or more or lesspartially oxidized and remaining in the converter,instead ofbeingfurther treated by addition of carburizing materials or materialsmore or less rich in manga- The metal thus more or less,

ncse, silicon, &c., in the converter itself, as is customary in makingBessemer steel, is poured either directly from the first apparatus intothe electric crucible or into a steel ladle or another like apparatus,and thence into the electric crucible, the metal being all the timefluid. The pouring shouldbe effected in such a manner that the liquidmetal runs into the electric crucible from the lower part of the vesselwhich contains it in order that the last portions of slag containingimpurities floating upon the metal may be retained in the vessel at theend of the pouring. The liquid metal is introduced into the cruciblewhile the latter is still hot, having either been heated for the purposeor from the preceding operation, and the electric current is passed soas to raise the temperature to the desired degree. The mass, whichgenerally contains more or less oxygen or oxid of iron, is kept in "astate of fusion by the heat of the electric are which supplies thenecessary calories. It

is now treated under the desired conditions for obtaining steel of thedesired quality. For example, there is introduced into the cruciblecarbon in the form of carburite (see French Patent No. 320,682, datedApri l 25, 1902) in order to deoxidize completely the metal and toproduce the degree of carburization proper to the quality of steeldesired. Equally well there may be added at a suitable moment alloys ormetals such as ferromanganese, ferronickel, ferrochrome, or chromium,nickel, tungsten, molybdenum, vanadium, &c.if it is desired to obtain asteel containing such metals.

This process permits of heating metal previously su peroxidized in aBessemer converter or the like without exposure to flame or a blast ofair (and consequent oxidation) to a higher temperature (1,9O0centigrade, as compared with 1,700 centigrade) and with a regularity andconsequent accurate control of composition which cannot be obtained inany other way. The effect of heating (due chiefly to the increasedchemical activity of the carbon) in the electric furnance as comparedwith a Bessemer converter is illustrated in the following table, whichshows for a given percentage of carbon the minimum content of oxygenwhich may be obtained with the Bessemer converter and the electricfurnace, respectively, (presuming an absence of manganese and siliconand the highest temperatures obtainable in the two apparatusz) Bessemer.Electric.

0 =O.75 O=O.30 0:0.50 0 =0 01 0:030 0:000 0:0.01 0 =0.00

In the Bessemer and open-hearth processes it is impossible to carry theoxidation sufficiently far to completely eliminate the impuritiesinitially present without leaving a considerable quantity of oxygen,which is well known as a most hurtful element, a metal entirely freefrom impurities being necessarily so superoxidized as to be practicallyor nearly useless according to the previously-employed methods ofdeoxidation, (such as treatment in the Siemens furnace or in thecrucible.) Such a superoxidized metal, however, is perfectly utilizablein the second stage of my process. For example, the following tableillustrates the percentage of impurities in good basic Bessemer steeland in a product of my process:

Bessemer. Heroult.

0.005 (to any desired maximum.) 0.000 (to any desired maximum.) 0.50 (toany desired maximum.)

wow

operations into two phases in order to con' duct the process which formsthe subject-matter of this application for the manufacture of iron andsteel in an electric furnace, not only is one able more completely tocontrol the reactions involved, but also one may effect a considerableeconomy of time and labor.- In fact, while the direct transformation ofcastiron into steel, including the purification, occupies more than fiveto six hours in the electric furnace the duration of the two treatmentsin the actual processthat is to say, successively in the Bessemerconverter and the electric furnacemay be reduced to onehalf that named.More particularly it may be noted that the operation in the Bessemerconverter being stopped after the oxidation takesless time than usual.Besides, the operation of conversion in the electric furnace isabbreviated, because the electrical energy is no longer required toeffect the decarburization and the purification; Moreover, if severalelectric crucibles or furnaces are to be worked at the same time eachmust be furnished with the electrical energy necessary for the firstphase of the operation, while the new method has the advantage that itis possible to feed several such electrical apparatus by a singleBessemer converter, so that the yield produced by an installation isindustrially much more considerable. To this end it is useful inpractice to arrange a Bessemer converter so that it may serve severalelectric crucibles or furnaces and in such a manner as to facilitaterapid transference of metal. WVith a single operation in the converterit is possible to feedfour' or six electric furnaces, and even more,according to the respective capacities of the converter and the electricfurnace. Finally it may be added that by this process the carburizationis effected in a more satisfactory manner and more surely in theelectric furnace, especially when the materials worked are phosphoric,since it is easy to remove the phosphoric slag completely during thetransference of the metal from the Bessemer converter to the electricfurnace.

The superoxidation referred to is especially of importance whenphosphoric pig is being treated in order to completely oxidize thephosphorus as stated above. In the ordinary Bessemer process, forexample, the oxidation is carried on until the flame disappears or issaid to drop- Substantially the whole of the carbon has then beenoxidized, and the continuation of the process beyond this pointconstitutes a superoxidation which distinguishes the present process asapplied to phosphoric pig.

The term cast-iron, as herein used, refers not only to the originalproduct of the blastfurnace, but to any other metal or mixture (usuallycontaining carbon and more or less silicon, manganese, sulfur, andphosphorus) requiring substantially the same operations to convert itinto iron or steel. The iron or steel product is one of exceptionalpurity, which purity forms the principal feature of advantage in theprocess.

I claim as my invention 1. A process for converting cast-iron or thelike into high-grade or crucible steel,which consists in first treatingthe metal in a Bessemer converter, then transferring it to an electricfurnace in which it is finally treated to deoxidize and carburize it,substantially as described.

2. A process for converting cast-iron or the like into high-grade orcrucible steel, which consists in first refining it by oxidation, andthen transforming it in an electric furnace into the desired product.

3. A process for converting cast-iron or the like into high-grade orcrucible -steel. which consists in first refining it by oxidation, andthen removing the slag and transferring the remainder to an electricfurnace and there deoxidizing and transforming it into the desiredproduct.

4. A process for converting cast-iron into iron or steel, which consistsin first refining it by oxidation until any phosphorus contained hasbeen practically completely oxidized, and then deoxidizing andtransforming it in an electric furnace into the desired product. v

5. A process for converting cast-iron or the like into iron or steel ofexceptional purity, which consists in first oxidizing it, continuing theoxidation until the mass is superoxidized beyond the point at whichsubstantially all the carbon has been oxidized, and then transforming itin an electric furnace into the desired product.

6. A process of converting cast-iron or the like into high-grade-orcrucible steel,which consists in first refining it by oxidation beyondthe point to which oxidation is ordinarily carried in the Bessemerprocess and until the content of harmful ingredients is sufiicientlyreduced for the manufacture of such steel, and then deoxidizing andtransforming it into steel ofthe desired composition in the electricfurnace.

7. A process for converting cast-iron or the like into high-grade orcrucible steel,which consists in first refining it by oxidation beyondthe point to which oxidation is ordinarily carried in the Bessemerprocess and until the content of harmful ingredients is sufficientlyreduced for the manufacture of such steel, and then oxidizing andtransforming it into steel of the desired composition under theapplication ofthe heat of an electricarc.

8. A process for converting cast-iron or the like into iron or steel,which consists in first refining it by oxidation until any phosphoruspresent has been practically completely oxidized, and then deoxidizingand transforming it into iron or steel of the desired composition underthe application of the heat of an electric are.

In witness whereof I have hereunto signed my name in the presence of twosubscribing witnesses.

PAUL LOUIS TOUSSAINT HEROULT.

Witnesses:

JULEs ARMENGAUD, J eune, MARoEL ARMENGAUD, J eune.

